25 hp johnson not running top speed

[Taylorsville]

Today we went out on the water and the motor would run great at full throttle then after a while the motor would run like it was in half throttle. Its a 1992 25 HP Johnson. What could it be?

 

[R Willis]

Re: 25 hp johnson not running top speed

Based upon my recent experience with a 1996 25 HP Johnson. I would question the fuel supply. Try squeezing the bulb on the gas hose while it is running. If it picks up speed then check the fuel pump.
RW

 

[Cofe]

Re: 25 hp johnson not running top speed

Is the motor overheating? Does it have a good tell tale stream?
Your motor will go into "slow mode" when a sensor in the head detects a overheat condition. The motor would then be limited to 2000 rpm.
If it is not overheating, I would suspect the high speed jet in the carb getting plugged up.

RWillis is right on about checking the fuel system.

 

[Taylorsville]

Re: 25 hp johnson not running top speed

the stream of water is coming out great and the carb was rebuilt last year. I am using the gas from last season it smelled good and has been in my garage for about 5 months so i thought it would be good. Could it be the gas? if so do you think if i put new gas in and some seafome that would fix the prob?

 

[Taylorsville]

Re: 25 hp johnson not running top speed

I will check the fuel pump as well.

 

[Cofe]

Re: 25 hp johnson not running top speed

A easy check is to remove the fuel line connection on the carb bowl, then clean out the high speed jet with a wire, like a bread tie with the plastic removed. The jet is small, and anything can plug it easily.

 

[Taylorsville]

Re: 25 hp johnson not running top speed

i just removed the cover and found som water sitting at the bottom. Could this be water in fuel problem?

 

[Cofe]

Re: 25 hp johnson not running top speed

Yep, Water will settle to the bottom of a tank, or carb bowl. Ethanol gas attracts water much more than regular gas.

 

[Taylorsville]

Re: 25 hp johnson not running top speed

water area. How do i fix the water prob?

 

[Timguy]

Re: 25 hp johnson not running top speed

Its true that ethanol will attract water, however the 10% ethanol will suspend its own weight in water as well. That is what makes it get rotten faster and turn over. In damp climates 6 months can really spell trouble. I recommend never storing your tank or outboard without running non oxy fuel on your last outing. Stabil alone is not the answer. I think maybe your high speed jet is restricted with gum from the old fuel and the spark plugs should be cleaned or replaced as old fuel raises trouble with plugs too. In most pre 2000 motors, ethanol will in time destroy any component containing rubber along with other materials used in gaskets, hoses, and seals.

 

[Cofe]

Re: 25 hp johnson not running top speed

Looks like carb slobber.
When the motor wasn't running right, the carb probably puked that stuff out. Did you put fuel stabilizer in your fuel last fall?

 

[Taylorsville]

Re: 25 hp johnson not running top speed

I did. but sounds like i should always start fresh each season.

 

[Cofe]

Re: 25 hp johnson not running top speed

Saw a old timer one time set his fuel tank on a picnic table and carefully insert a quarter inch tygon tube line into the tank and hold it real close to the bottom. He then siphoned the water out of the bottom of the tank. He said he did it every year. LoL.....I have never tried it though.....

 

[Taylorsville]

Re: 25 hp johnson not running top speed

well im not going to do that. I will despose of the fule. Will this be okay to sit like this till weekend? I cant get in to it till then.

 

[Cofe]

Re: 25 hp johnson not running top speed

Yes it would be ok, but you are going to have to purge all your fuel lines and also clean the carb bowl. I would also mention to clean that high speed jet at the same time.

 

[Taylorsville]

Re: 25 hp johnson not running top speed

Thats why i want to wait till weekend. I i can do it right!!

 

[tx1961whaler]

Re: 25 hp johnson not running top speed

Today we went out on the water and the motor would run great at full throttle then after a while the motor would run like it was in half throttle. Its a 1992 25 HP Johnson. What could it be?

Or it could be that you're running on 1 cylinder. Check for spark when it cuts out. Maybe change the spark plugs.

 

[Taylorsville]

Re: 25 hp johnson not running top speed

Im going to clean out the fuel lines and carb bowl, put new spark plugs in and get new fuel

 

[Taylorsville]

Re: 25 hp johnson not running top speed

when you say flush the lines do you mean take them apart and force new fuel through them? thats what i am planing to do unless there is a different way.

 

[Taylorsville]

Re: 25 hp johnson not running top speed

Okay everyone, Here is the deal. I took the carb off today when I lowered the bowl I saw no water in there the gas look clean also. I took it all apart it was all very clean (as I thought it would be because it was rebuilt last season) spark plugs looked a little gunky so I think I will get new ones. But the question is were do you think the water came from as shown in the pictures? Could that just be a fluke thing? I'm going to go ahead and get new gas anyways I just want to make sure I am not missing anything. And could this prob be only spark plugs? How gunky do they have to be before they start acting up?

I predered new plugs and a fuel pump repair kit both were cheap so i figured why not


not great pics hope they will do.